A laser printer often includes a toner cartridge and paper handling components. The toner cartridge can include a digital light emitter, photoconductor drum, a charge roller, a developer roller, a developer blade, a toner transfer roller, a toner storage unit, and a paper handling roller. The paper handling roller can include an exit roller and a fuser roller. During printing, the toner transfer roller supplies toner to the developer roller, and the developer blade forms the toner into a thin, even layer on the surface of the developer roller. The charge roller charges the photoconductive drum with a negative charge. After the photoconductive drum has been exposed to a light emitter, the surface of the photoconductor drum forms an electrostatic latent image, and the developer roller transfers toner to the portion of the drum surface to form the toner image. The laser printer may also include a toner-removal wiper that removes excess toner from the surface of the developer roller after the developer roller has contacted the photoconductor drum. The toner on the drum subsequently is transferred to paper, and then fuses to form the print.
The developer roller is cylindrical and typically includes a central shaft surrounded by a synthetic rubber or urethane elastomer portion. U.S. Pat. Nos. 6,352,771 and 6,780,364 to Chiang et al., both of which are incorporated by reference herein in their entirety, describe developer rollers fabricated with a conductive urethane formed by dissolving metal salts in urethane precursors including polyether polyols and/or polyether polyamines and then reacting the urethane precursors with diphenylmethane diisocyanate. The resulting urethane has a resistivity between 1E6 Ω·cm (i.e., 1×106 Ω·cm) and 9E8 Ω·cm (i.e., 9×108 Ω·cm) and a hardness between 30 Shore A and 50 Shore A on cube.